Upgrading went smooth with no problems, but the divace fails to boot, shows an error message: "Recovery System v5.0 E:failed to mount /metadata /dev/block/platform/ff0f0000.rskdmmc/by-name/metadata (Invalid argument)"

I downgraded the firmware to MK902II FW_161021 and this one works fine.

The conclusion is that MK902II Android 5.1 FW_170808 do not work.Does anyone know how to make it working?